hi. me and a couple of my uncles are trying to fix my 1990 honda accord lx 4dr. when i bought it it workes fine. couple of months later i noticed that during the heat. the car would not want to start, and if it did start, the rpm needle will be going up and down like if i was pressing on the gas. now the whole car wont start. were currently checking the main relay. any ideaz?


thnx alot.

 

Fuel pressure can be checked by cracking open the test port fitting at the fuel rail; when the key is turned on the fuel pump should run for about 3 seconds.

The ignition switch should put thru battery power to the Black/yellow wire at the dist. when the key is on or in crank.

Check for spark out to the spark plugs by grounding an old plug and have someone crank the engine.

Check timing to be sure the T-belt hasn't sheared teeth and is in proper time.

These are basic checks to help you get on the right track.

I seriously doubt the T-stat is causing this problem

 

Once you get it started here is for your fluxing idle,

High Idle speed and Fluctuation troubleshooting

Leaking EACV- Disconnect EACV connector. Idle speed should decrease. With the connector disconnected block the hole in the intake port or pinch the hose from the air cleaner to the EACV. If the idle speed decreases the valve is leaking. This condition will not set a code. The ECM can only detect an open or short circuit. It also may clog it’s screen if it has one.

Leaking IAC- (Idle air control valve) Disconnect IAC connector. Idle speed should decrease. With the connector disconnected, block the hole or pinch the hose to the IAC valve. If the idle speed decreases the valve is leaking. May not set a code and may not be a codeable circuit on all models.

TW or ECT sensor- (engine coolant temperature sensor) voltage should be about 3.0 volts @ 60 deg F and between .55 & .7 volts @ normal operating temp. If the voltage is above .8 volts at normal operating temp, will cause rich mixture and high idle speed. May not set a code because it is not far enough out of its operating parameters. **Also this sensor will not read temperature correctly if coolant is low. (beware)

Vacuum leaks- a loose vacuum hose or leaking intake manifold gasket can cause high idle speed and/or fluctuation. Also check for bad PCV valve.

Fast Idle Valve- (if equipped) a fast idle valve that is sticking can cause high idle speed and fluctuation. Check it by removing the steel cap on the top and putting your finger over the hole in the middle of the seat under the cap or block the port just inside of the throttle body opening, when the Idle is fluctuating or staying high. When the engine is warm this valve should be closed. You can tighten the seat but it will also change the idle speed warm up values (closing).

Throttle valve- throttle position sensor voltage should be .5 volts with the throttle closed. Make sure the throttle valve is fully closed and voltage is within spec.

ECU-If all else is good, if you reset the ECU and the problem goes away temporarily, the ECU may be defective.